Tuesday, October 7, 2008

Platter Persistence

Over the last year, I have made what seems like a ton of casseroles, platters, plates, and other pieces with a large footprint on the kiln shelf. At first I had a problem with the pieces warping in the bisque load. After many loads, many pieces, and many clay bodies of warped or distorted pieces, I finally settled on wadding each piece during the bisque firing. I have now achieved non warped bisque pieces almost every time. Along the way, most folks told me to just give up, that flat bottomed platters and casseroles were hard to achieve success in Cone 10 firings and I should just make some vases or bowls. I'm not one to give up and am persistent. Somehow I knew it could be done.

Once I achieved success with my bisque pieces, I was so happy, now I could move on to decorating or glazing them in unique ways, I felt so lucky. So I spent lots of time with glazing experiments with this or that glaze or some special technique, only to have my beautiful pieces warp in the glaze firing, but not always. The bread bowl you see above is one of the few platters or casseroles with a nice glaze that didn't warp. Some would warp, but then the next load would be successful in the glaze firing. Of course, many of the most beautifully glazed pieces were the ones that warped. Maybe not so lucky.

Most of my pieces are slab built and some are made on slump molds. I was slowly learning firsthand that clay has a memory. Now you might already know this, but I've had to discover this the hard way. I had heard or read this phrase, but didn't quite know what it meant. I don't have a lot of clay resources around me and no one I spoke with seemed to be able to give me any reliable advice. Not wanting to give up, I forged on. Now I roll my clay thick in one direction and then insert a shim in the slab roller, turn the slab of clay 45 degrees and roll the clay in the other direction. I also found out how I dry the pieces is important too. Drying the casseroles on cake rakes wasn't always a good idea because the cake rakes are sometimes bowed, which made the casserole bow. Oh, do you see the bean bags, those help to hold the middle of the casserole flat while it is drying. So I have found better ways to dry my pieces. This has helped to minimize the warping in almost every bisque load. How lucky can I be.

This week I have another group of platters, casseroles, plates, bowls and other flat bottomed pieces which have come through the bisque load with shining colors. Some of my best pieces yet. Every one of these is almost perfect - no warping or cracking. I even have a couple of sets of plates that I can stack together they are so perfectly bisqued. This is a real accomplishment for me. Some of the bisque pieces have slight color differences in the clay body due to kiln temperature variations, but I'm hoping the glaze firing should equalize this. I adorned some of these pieces with under glaze, which came out quite well as far as I can tell. How lucky I am.

After the last glaze load with almost every platter warped, I am a bit kiln shy for the glaze load - OK I am really scared, nervous, frustrated and lots of other emotions rolled in there too. These current pieces all look so good, maybe I can just put some shellac over them and they'll be done - what do you think? No, OK, I guess I have to move forward.

The last load I wadded the glaze load pieces and they warped pretty bad, so now I have abandoned wadding of the glaze load. I am now going to put some porcelain sand on the kiln shelf with the idea that the sand will allow the piece to move freely as it heats up and relaxes back to where it wants to be when it cools down. Sound like a good theory? If you have any better ideas, now is the time to chime in. Glaze load is not loaded yet. This black casserole with blue under glaze will be going into the glaze load this week.

One more thing. I painted under glaze on some dark clay body pieces (the casserole and the undulating plate above for example) with the idea of putting a clear glaze over the top of them. I thought wouldn't it be beautiful to see the under glaze and at the same time see the dark clay body. Good idea right! Well, I just learned most clear glazes, if not all, have feldspar in them and feldspar reacts with the iron in the clay body and makes the clear glaze turn gray - another theory down the drain. Here is a photo of what a transparent glaze looks like on a Rod's Mix clay body. A medium tan body with some iron in it. The glaze takes on a gray cast with black specks. Not exactly what I am looking for with dark brown or black clay with under glaze. But I am moving on.

I am still going to try two different clear glazes on the dark clay bodies and I am also going to try a very thin celadon glaze on the dark clay body. I know most celadon is put on porcelain and light clay bodies, but I like to experiment and who knows I might get something really unique. You are probably wondering why I am not trying all this on test tiles. Well, we only have so much room on the shelves of the studio and so many firings, so if I don't get them in the load now, I may never get them fired in the glaze load. So I am experimenting with my pieces rather than test tiles. Above you see the Non Iron Blue Celadon Glaze on a porcelain clay body. We shall see what it looks like on a dark brown clay body.

Tomorrow I will be mixing up my two clear glazes and deciding how I will glaze all my pieces. What do you think? Do you have any experiences with dark clay bodies using a clear or celadon glaze? How about under glazes, what do you use to glaze over them? How about ideas on kiln loading to minimize warping and enhance air flow? Please let me know, I'd love to hear your thoughts. Any and all ideas are welcome.


  1. sometimes clears look a little cloudy on a dark clay, not sure I can anything else----
    but anyway, that is the first time I have seen the bean bags, tres clever! TRES CUTE platters too!

  2. Keep it up; my partner Lana makes platters and large cone 10 pieces and has been through it all..her porcelain mother bowls are extremely large and she has many that come through the process ok. You are becoming a potter and as they say, as much goes into the smashed pile as goes on the keeper shelf.
    Stick with it potter girl.. Joan Tucker Off Center Productions

  3. Hi Gary, Thanks for the info. I just ready on Clay Times that Laguna Clear #16 is good over oxides. I may try that one.

    Hi Joan, Thank you for your support. Do you have those mother bowls posted on your site? I'll have to check back again. Someone in class suggested I make a mosaic out of some of the platters; I may try that in my free time - not sure when that will be though.

  4. Hi Joan, I got on your website again. I guess I didn't realize just how large those bowls were when I looked before. Ok, now I have hope. thanks again.


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